In recent years, solar cells directly converting solar energy into electrical energy have been increasingly expected as next-generation energy sources particularly from the viewpoint of global environmental issues. In particular, solar cells that are most commonly manufactured and marketed at present have a configuration in which an electrode is placed on each of a light-receiving surface on which sunlight is incident and a back surface which is opposite to the light-receiving surface.
However, in the case of forming an electrode on a light-receiving surface, the amount of incident sunlight is reduced by an amount corresponding to the area of the electrode because sunlight is reflected and absorbed by the electrode. Therefore, a back contact-type solar cell in which electrodes are placed only on a back surface is being developed (refer to, for example, Patent Literature 1).
FIG. 15 shows a schematic sectional view of a conventional back contact-type solar cell described in Patent Literature 1. The back contact-type solar cell shown in FIG. 15 has a configuration in which an i-type amorphous semiconductor layer 117i, an n-type amorphous semiconductor layer 117n, and an insulating layer 116 are stacked on a light-receiving surface of a crystalline semiconductor substrate 111 having an n- or p-conductivity type in that order.
An IN stack 112 is placed on the back surface of the crystalline semiconductor substrate 111. The IN stack 112 has a configuration in which an i-type amorphous semiconductor layer 112i and an n-type amorphous semiconductor layer 112n are stacked on the crystalline semiconductor substrate 111 in that order.
Furthermore, an IP stack 113 is placed on the back surface of the crystalline semiconductor substrate 111. The IP stack 113 has a configuration in which an i-type amorphous semiconductor layer 113i and a p-type amorphous semiconductor layer 113p are stacked on the crystalline semiconductor substrate 111 in that order.
An n-side electrode 114 and p-side electrodes 115 are formed as described below. That is, a conductive layer (not shown) is formed over the back surface of the crystalline semiconductor substrate 111 by a thin-film formation process such as a CVD (chemical vapor deposition) process including a plasma CVD process or a sputtering process. Next, the conductive layer is divided by a lithographic process or the like. Thereafter, a coating layer is formed on the conductive layer. Incidentally, the n-side electrode 114 and the p-side electrodes 115 are electrically separated by trenches 119 placed on an insulating layer 118 on the back surface of the crystalline semiconductor substrate 111.
As shown in FIG. 15, in the conventional back contact-type solar cell, the n-side electrode 114 and the p-side electrodes 115 are not placed in a peripheral portion 110a2 of the back surface of the crystalline semiconductor substrate 111 but are placed only in a region 110al excluding the peripheral portion 110a2. This is because the peripheral portion 110a2, which is not provided with any electrode, is necessary as a region for fixing the crystalline semiconductor substrate 111 during the formation of the n-side electrode 114 and the p-side electrodes 115.